[p5sagit/p5-mst-13.2.git] / lib / Net / Ping / README

NAME
    Net::Ping - check a remote host for reachability

    $Id: Ping.pm,v 1.13 2001/12/07 02:18:44 rob Exp $

SYNOPSIS
        use Net::Ping;

        $p = Net::Ping->new();
        print "$host is alive.\n" if $p->ping($host);
        $p->close();

        $p = Net::Ping->new("icmp");
        foreach $host (@host_array)
        {
            print "$host is ";
            print "NOT " unless $p->ping($host, 2);
            print "reachable.\n";
            sleep(1);
        }
        $p->close();

        $p = Net::Ping->new("tcp", 2);
        # Try connecting to the www port instead of the echo port
        $p->{port_num} = getservbyname("http", "tcp");
        while ($stop_time > time())
        {
            print "$host not reachable ", scalar(localtime()), "\n"
                unless $p->ping($host);
            sleep(300);
        }
        undef($p);

        # For backward compatibility
        print "$host is alive.\n" if pingecho($host);

DESCRIPTION
    This module contains methods to test the reachability of remote hosts on
    a network. A ping object is first created with optional parameters, a
    variable number of hosts may be pinged multiple times and then the
    connection is closed.

    You may choose one of four different protocols to use for the ping. The
    "udp" protocol is the default. Note that a live remote host may still
    fail to be pingable by one or more of these protocols. For example,
    www.microsoft.com is generally alive but not pingable.

    With the "tcp" protocol the ping() method attempts to establish a
    connection to the remote host's echo port. If the connection is
    successfully established, the remote host is considered reachable. No
    data is actually echoed. This protocol does not require any special
    privileges but has higher overhead than the other two protocols.

    Specifying the "udp" protocol causes the ping() method to send a udp
    packet to the remote host's echo port. If the echoed packet is received
    from the remote host and the received packet contains the same data as
    the packet that was sent, the remote host is considered reachable. This
    protocol does not require any special privileges. It should be borne in
    mind that, for a udp ping, a host will be reported as unreachable if it
    is not running the appropriate echo service. For Unix-like systems see
    the inetd(8) manpage for more information.

    If the "icmp" protocol is specified, the ping() method sends an icmp
    echo message to the remote host, which is what the UNIX ping program
    does. If the echoed message is received from the remote host and the
    echoed information is correct, the remote host is considered reachable.
    Specifying the "icmp" protocol requires that the program be run as root
    or that the program be setuid to root.

    If the "external" protocol is specified, the ping() method attempts to
    use the `Net::Ping::External' module to ping the remote host.
    `Net::Ping::External' interfaces with your system's default `ping'
    utility to perform the ping, and generally produces relatively accurate
    results. If `Net::Ping::External' if not installed on your system,
    specifying the "external" protocol will result in an error.

  Functions

    Net::Ping->new([$proto [, $def_timeout [, $bytes]]]);
        Create a new ping object. All of the parameters are optional. $proto
        specifies the protocol to use when doing a ping. The current choices
        are "tcp", "udp" or "icmp". The default is "udp".

        If a default timeout ($def_timeout) in seconds is provided, it is
        used when a timeout is not given to the ping() method (below). The
        timeout must be greater than 0 and the default, if not specified, is
        5 seconds.

        If the number of data bytes ($bytes) is given, that many data bytes
        are included in the ping packet sent to the remote host. The number
        of data bytes is ignored if the protocol is "tcp". The minimum (and
        default) number of data bytes is 1 if the protocol is "udp" and 0
        otherwise. The maximum number of data bytes that can be specified is
        1024.

    $p->ping($host [, $timeout]);
        Ping the remote host and wait for a response. $host can be either
        the hostname or the IP number of the remote host. The optional
        timeout must be greater than 0 seconds and defaults to whatever was
        specified when the ping object was created. If the hostname cannot
        be found or there is a problem with the IP number, undef is
        returned. Otherwise, 1 is returned if the host is reachable and 0 if
        it is not. For all practical purposes, undef and 0 and can be
        treated as the same case.

    $p->open($host);
        When you are using the stream protocol, this call pre-opens the tcp
        socket. It's only necessary to do this if you want to provide a
        different timeout when creating the connection, or remove the
        overhead of establishing the connection from the first ping. If you
        don't call `open()', the connection is automatically opened the
        first time `ping()' is called. This call simply does nothing if you
        are using any protocol other than stream.

    $p->open($host);
        When you are using the stream protocol, this call pre-opens the tcp
        socket. It's only necessary to do this if you want to provide a
        different timeout when creating the connection, or remove the
        overhead of establishing the connection from the first ping. If you
        don't call `open()', the connection is automatically opened the
        first time `ping()' is called. This call simply does nothing if you
        are using any protocol other than stream.

    $p->close();
        Close the network connection for this ping object. The network
        connection is also closed by "undef $p". The network connection is
        automatically closed if the ping object goes out of scope (e.g. $p
        is local to a subroutine and you leave the subroutine).

    pingecho($host [, $timeout]);
        To provide backward compatibility with the previous version of
        Net::Ping, a pingecho() subroutine is available with the same
        functionality as before. pingecho() uses the tcp protocol. The
        return values and parameters are the same as described for the
        ping() method. This subroutine is obsolete and may be removed in a
        future version of Net::Ping.

WARNING
    pingecho() or a ping object with the tcp protocol use alarm() to
    implement the timeout. So, don't use alarm() in your program while you
    are using pingecho() or a ping object with the tcp protocol. The udp and
    icmp protocols do not use alarm() to implement the timeout.

NOTES
    There will be less network overhead (and some efficiency in your
    program) if you specify either the udp or the icmp protocol. The tcp
    protocol will generate 2.5 times or more traffic for each ping than
    either udp or icmp. If many hosts are pinged frequently, you may wish to
    implement a small wait (e.g. 25ms or more) between each ping to avoid
    flooding your network with packets.

    The icmp protocol requires that the program be run as root or that it be
    setuid to root. The other protocols do not require special privileges,
    but not all network devices implement tcp or udp echo.

    Local hosts should normally respond to pings within milliseconds.
    However, on a very congested network it may take up to 3 seconds or
    longer to receive an echo packet from the remote host. If the timeout is
    set too low under these conditions, it will appear that the remote host
    is not reachable (which is almost the truth).

    Reachability doesn't necessarily mean that the remote host is actually
    functioning beyond its ability to echo packets. tcp is slightly better
    at indicating the health of a system than icmp because it uses more of
    the networking stack to respond.

    Because of a lack of anything better, this module uses its own routines
    to pack and unpack ICMP packets. It would be better for a separate
    module to be written which understands all of the different kinds of
    ICMP packets.

AUTHOR(S)
      Current maintainer Net::Ping base code:
        colinm@cpan.org (Colin McMillen)

      Stream protocol:
        bronson@trestle.com (Scott Bronson)

      Original pingecho():
        karrer@bernina.ethz.ch (Andreas Karrer)
        pmarquess@bfsec.bt.co.uk (Paul Marquess)

      Original Net::Ping author:
        mose@ns.ccsn.edu (Russell Mosemann)

      Compatibility porting:
        bbb@cpan.org (Rob Brown)

COPYRIGHT
    Copyright (c) 2001, Colin McMillen. All rights reserved. Copyright (c)
    2001, Rob Brown. All rights reserved.

    This program is free software; you may redistribute it and/or modify it
    under the same terms as Perl itself.
Commit	Line	Data
505f3f16	1	NAME
	2	Net::Ping - check a remote host for reachability
	3
	4	$Id: Ping.pm,v 1.13 2001/12/07 02:18:44 rob Exp $
	5
	6	SYNOPSIS
	7	use Net::Ping;
	8
	9	$p = Net::Ping->new();
	10	print "$host is alive.\n" if $p->ping($host);
	11	$p->close();
	12
	13	$p = Net::Ping->new("icmp");
	14	foreach $host (@host_array)
	15	{
	16	print "$host is ";
	17	print "NOT " unless $p->ping($host, 2);
	18	print "reachable.\n";
	19	sleep(1);
	20	}
	21	$p->close();
	22
	23	$p = Net::Ping->new("tcp", 2);
	24	# Try connecting to the www port instead of the echo port
	25	$p->{port_num} = getservbyname("http", "tcp");
	26	while ($stop_time > time())
	27	{
	28	print "$host not reachable ", scalar(localtime()), "\n"
	29	unless $p->ping($host);
	30	sleep(300);
	31	}
	32	undef($p);
	33
	34	# For backward compatibility
	35	print "$host is alive.\n" if pingecho($host);
	36
	37	DESCRIPTION
	38	This module contains methods to test the reachability of remote hosts on
	39	a network. A ping object is first created with optional parameters, a
	40	variable number of hosts may be pinged multiple times and then the
	41	connection is closed.
	42
	43	You may choose one of four different protocols to use for the ping. The
	44	"udp" protocol is the default. Note that a live remote host may still
	45	fail to be pingable by one or more of these protocols. For example,
	46	www.microsoft.com is generally alive but not pingable.
	47
	48	With the "tcp" protocol the ping() method attempts to establish a
	49	connection to the remote host's echo port. If the connection is
	50	successfully established, the remote host is considered reachable. No
	51	data is actually echoed. This protocol does not require any special
	52	privileges but has higher overhead than the other two protocols.
	53
	54	Specifying the "udp" protocol causes the ping() method to send a udp
	55	packet to the remote host's echo port. If the echoed packet is received
	56	from the remote host and the received packet contains the same data as
	57	the packet that was sent, the remote host is considered reachable. This
	58	protocol does not require any special privileges. It should be borne in
	59	mind that, for a udp ping, a host will be reported as unreachable if it
	60	is not running the appropriate echo service. For Unix-like systems see
	61	the inetd(8) manpage for more information.
	62
	63	If the "icmp" protocol is specified, the ping() method sends an icmp
	64	echo message to the remote host, which is what the UNIX ping program
65	does. If the echoed message is received from the remote host and the
66	echoed information is correct, the remote host is considered reachable.
67	Specifying the "icmp" protocol requires that the program be run as root
68	or that the program be setuid to root.
69
70	If the "external" protocol is specified, the ping() method attempts to
71	use the `Net::Ping::External' module to ping the remote host.
72	`Net::Ping::External' interfaces with your system's default `ping'
73	utility to perform the ping, and generally produces relatively accurate
74	results. If `Net::Ping::External' if not installed on your system,
75	specifying the "external" protocol will result in an error.
76
77	Functions
78
79	Net::Ping->new([$proto [, $def_timeout [, $bytes]]]);
80	Create a new ping object. All of the parameters are optional. $proto
81	specifies the protocol to use when doing a ping. The current choices
82	are "tcp", "udp" or "icmp". The default is "udp".
83
84	If a default timeout ($def_timeout) in seconds is provided, it is
85	used when a timeout is not given to the ping() method (below). The
86	timeout must be greater than 0 and the default, if not specified, is
87	5 seconds.
88
89	If the number of data bytes ($bytes) is given, that many data bytes
90	are included in the ping packet sent to the remote host. The number
91	of data bytes is ignored if the protocol is "tcp". The minimum (and
92	default) number of data bytes is 1 if the protocol is "udp" and 0
93	otherwise. The maximum number of data bytes that can be specified is
94	1024.
95
96	$p->ping($host [, $timeout]);
97	Ping the remote host and wait for a response. $host can be either
98	the hostname or the IP number of the remote host. The optional
99	timeout must be greater than 0 seconds and defaults to whatever was
100	specified when the ping object was created. If the hostname cannot
101	be found or there is a problem with the IP number, undef is
102	returned. Otherwise, 1 is returned if the host is reachable and 0 if
103	it is not. For all practical purposes, undef and 0 and can be
104	treated as the same case.
105
106	$p->open($host);
107	When you are using the stream protocol, this call pre-opens the tcp
108	socket. It's only necessary to do this if you want to provide a
109	different timeout when creating the connection, or remove the
110	overhead of establishing the connection from the first ping. If you
111	don't call `open()', the connection is automatically opened the
112	first time `ping()' is called. This call simply does nothing if you
113	are using any protocol other than stream.
114
115	$p->open($host);
116	When you are using the stream protocol, this call pre-opens the tcp
117	socket. It's only necessary to do this if you want to provide a
118	different timeout when creating the connection, or remove the
119	overhead of establishing the connection from the first ping. If you
120	don't call `open()', the connection is automatically opened the
121	first time `ping()' is called. This call simply does nothing if you
122	are using any protocol other than stream.
123
124	$p->close();
125	Close the network connection for this ping object. The network
126	connection is also closed by "undef $p". The network connection is
127	automatically closed if the ping object goes out of scope (e.g. $p
128	is local to a subroutine and you leave the subroutine).
129
130	pingecho($host [, $timeout]);
131	To provide backward compatibility with the previous version of
132	Net::Ping, a pingecho() subroutine is available with the same
133	functionality as before. pingecho() uses the tcp protocol. The
134	return values and parameters are the same as described for the
135	ping() method. This subroutine is obsolete and may be removed in a
136	future version of Net::Ping.
137
138	WARNING
139	pingecho() or a ping object with the tcp protocol use alarm() to
140	implement the timeout. So, don't use alarm() in your program while you
141	are using pingecho() or a ping object with the tcp protocol. The udp and
142	icmp protocols do not use alarm() to implement the timeout.
143
144	NOTES
145	There will be less network overhead (and some efficiency in your
146	program) if you specify either the udp or the icmp protocol. The tcp
147	protocol will generate 2.5 times or more traffic for each ping than
148	either udp or icmp. If many hosts are pinged frequently, you may wish to
149	implement a small wait (e.g. 25ms or more) between each ping to avoid
150	flooding your network with packets.
151
152	The icmp protocol requires that the program be run as root or that it be
153	setuid to root. The other protocols do not require special privileges,
154	but not all network devices implement tcp or udp echo.
155
156	Local hosts should normally respond to pings within milliseconds.
157	However, on a very congested network it may take up to 3 seconds or
158	longer to receive an echo packet from the remote host. If the timeout is
159	set too low under these conditions, it will appear that the remote host
160	is not reachable (which is almost the truth).
161
162	Reachability doesn't necessarily mean that the remote host is actually
163	functioning beyond its ability to echo packets. tcp is slightly better
164	at indicating the health of a system than icmp because it uses more of
165	the networking stack to respond.
166
167	Because of a lack of anything better, this module uses its own routines
168	to pack and unpack ICMP packets. It would be better for a separate
169	module to be written which understands all of the different kinds of
170	ICMP packets.
171
172	AUTHOR(S)
173	Current maintainer Net::Ping base code:
174	colinm@cpan.org (Colin McMillen)
175
176	Stream protocol:
177	bronson@trestle.com (Scott Bronson)
178
179	Original pingecho():
180	karrer@bernina.ethz.ch (Andreas Karrer)
181	pmarquess@bfsec.bt.co.uk (Paul Marquess)
182
183	Original Net::Ping author:
184	mose@ns.ccsn.edu (Russell Mosemann)
185
186	Compatibility porting:
187	bbb@cpan.org (Rob Brown)
188
189	COPYRIGHT
190	Copyright (c) 2001, Colin McMillen. All rights reserved. Copyright (c)
191	2001, Rob Brown. All rights reserved.
192
193	This program is free software; you may redistribute it and/or modify it
194	under the same terms as Perl itself.
195